The subject matter of the present invention relates generally to liquid tank filler cap and valve assembly and, in particular, to a vented fuel tank cap and valve assembly including a pressure relief valve with a main valve member mounted at a main vent opening through such cap which is normally spring-biased closed and which includes a fusible element that melts above a predetermined temperature to cause the valve to open. The fuel tank cap and valve assembly may also include a float valve mounted at a secondary vent passage through the valve stem of the main valve member that is normally open to vent fumes from the tank but which closes to prevent spillage when the liquid fuel raises within the tank such as when a truck with such tank travels rapidly around a corner.
It is known to provide a fuel tank cap and valve assembly including a spring-biased pressure relief valve mounted on such cap as shown in U.S. Pat. No. 3,918,606 of Keller issued Nov. 11, 1975; U.S. Pat. No. 4,294,376 of Keller issued Oct. 13, 1981; and U.S. Pat. No. 4,091,955 of Sloan issued May 30, 1978. In addition, it is known to provide a tank vent with a float valve for closing the vent when the tank is tipped as shown in U.S. Pat. No. 3,970,098 of Boswank, et al., issued July 20, 1976, and U.S. Pat. No. 4,325,398 of Green issued Apr. 20, 1982. These patents also show that it is old to provide a spherical steel ball as a weight member for closing the float valve in an inverted position of the tank so that it also functions as a gravity valve. They also show that it is old to provide vents with plugs or cover assemblies having fusible elements which melt above a predetermined temperature to open the vent.
It has previously been proposed to provide a fuel tank cap with both a pressure-relief valve and a gravity-actuated valve as shown in U.S. Pat. No. 3,985,260 of Evans issued Oct. 12, 1976, and U.S. Pat. No. 4,162,021 of Crute issued July 24, 1979. Also, it is old to provide a fuel tank vent with a float valve separate from the tank cap including a hollow float member with a bottom opening cavity as shown in U.S. Pat. No. 3,910,302 of Sudhir issued Oct. 7, 1975. In addition, it has also been proposed to provide a discharge prevention valve in the fuel tank filler neck itself, as shown in U.S. Pat. No. 3,610,263 of Walters issued Oct. 5, 1971. Finally, it has been previously suggested to provide a valve assembly for a fuel tank including a vent passage with both a rollover float valve and a pressure-relief valve which are both spring operated as shown in U.S. Pat. No. 4,351,350 of Crute issued Sept. 28, 1982.
These prior patented devices have extremely complicated valve assemblies and are not of a simple, trouble-free, compact construction like that of the present invention which is suitable for mounting on a fuel tank cap. In addition, such prior fuel tank cap and valve assembly apparatus are not provided with a fusible element as part of the valve assembly which melts above a predetermined pressure to open the valve in the event of a fire in the manner of the present invention. Furthermore, none of such fuel tank cap and valve assembly apparatus employs a pressure-relief valve for a main vent opening in the tank cap having an auxiliary seal means provided on the main valve member at a position spaced inwardly of the main valve seal for maintaining the valve closed, even after the fusible length melts, until the pressure within the tanks exceeds a predetermined minimum amount to open both of such seals. Finally, none of these prior patents shows such a fuel tank cap and valve assembly having a float valve mounted within a valve cage attached to the valve stem of the pressure-relief valve for closing a secondary vent passage through such valve stem like the invention here. Also, none of such patents shows the use of a hollow float valve member whose bottom opening is engaged by a metal ball in an inverted position to trap liquid within the cavity so that when the fuel tank is returned to a normal, upright position such liquid fuel flows out of the hollow float, causing it to open and preventing the valve from sticking, in the manner of the present invention.